A novel route for the production of chitosan/poly(lactide-co-glycolide) graft copolymers for electrospinning

Both chitosan and polylactide/polyglycolide have good biocompatibility and can be used to produce tissue engineering scaffolds for cultured cells. However the synthetic scaffolds lack groups that would facilitate their modification, whereas chitosan has extensive active amide and hydroxyl groups which would allow it to be subsequently modified for the attachment of peptides, proteins and drugs. Also chitosan is very hydrophilic, whereas PLGA is relatively hydrophobic. Accordingly there are many situations where it would be ideal to have a copolymer of both, especially one that could be electrospun to provide a versatile range of scaffolds for tissue engineering. Our aim was to develop a novel route of chitosan-g-PLGA preparation and evaluate the copolymers in terms of their chemical characterization, their performance on electrospinning and their ability to support the culture of fibroblasts as an initial biological evaluation of these scaffolds. Chitosan was first modified with trimethylsilyl chloride, and catalyzed by dimethylamino pyridine. PLGA-grafted chitosan copolymers were prepared by reaction with end-carboxyl PLGA (PLGA-COOH). FT-IR and(1)H-NMR characterized the copolymer molecular structure as being substantially different to that of the chitosan or PLGA on their own. Elemental analysis showed an average 18 pyranose unit intervals when PLGA-COOH was grafted into the chitosan molecular chain. Differential scanning calorimetry results showed that the copolymers had different thermal properties from PLGA and chitosan respectively. Contact angle measurements demonstrated that copolymers became more hydrophilic than PLGA. The chitosan-g-PLGA copolymers were electrospun to produce either nano- or microfibers as desired. A 3D fibrous scaffold of the copolymers gave good fibroblast adhesion and proliferation which did not differ significantly from the performance of the cells on the chitosan or PLGA electrospun scaffolds. In summary this work presents a methodology for making a hybrid material of natural and synthetic polymers which can be electrospun and reacts well as a substrate for cell culture.